Need Some Help

Good Day All

Long time reader of this forum and subscriber to Dangar Stu videos needs some help.

I bought a used 1991, Mercury 75 hp, ELPTO, serial number, D095679 that I need some help with.

As per a lot of the forums here, the engine bogs down at WOT. It starts fine and idles all day long. I can run the boat to about 3/4 throttle then it will bog down and sometimes comes back up in rpm. I can go to neutral and then start over but I cant get to full rpm. Here is what I've done with it.

Rebuilt and cleaned carbs
replaced all fuel and enrichment lines
Compression test 115,115, 120
Replaced coil for one cylinder
Replaced switch box
Stator and Trigger show ok on Ohms test
New gas tank and all lines from it to motor.
Primer is hard and squeezing it has not effect on problem
Exhaust tube ans tower is clear of obstructions
timed engine with light
Replaced water manifold gasket
Checked thermostat and pop it
New Plugs


For some reason I feel it my be an ignition issue or a water gasket issue?? I have had the carbs apart several times and there is nothing in them that would cause the problem.

Could the fly wheel key be broken off? It this point I'm waiting for a puller to check. Could water be coming in somewhere and cause this? Also is there any checks that would test the gaskets for the motor without taking it apart? The bolts that hold the motor to the lower unit are old and rusty I think they will break if I try to remove them.

Any help is appreciated.

Thanks

.."Could the fly wheel key be broken off?"

No, or it would not run.

Before pulling your hair out, try this: Warm the motor thoroughly, then put it in gear (boat on the trailer or tied to a dock). Adjust the idle mixture screws--SLOWLY and carefully, waiting several seconds after each TINY adjustment to let it settle out--until you get the best idle (which is usually the fastest idle). Then add 1/4 turn OUT (CCW) on thel idle screws and take her for a ride. If it's better,but still hesitates, add one additional 1/4 turn OUT.

Good luck!

Jeff

Thank you, Jeff.

I'll give it a try. I never thought an idle screw could effect the WOT.

Thanks again